Research On Dual Capacitance LNG Liquid Level Intelligent Sensor

China's environmental air quality is worsening with the development of industrialization and urbanization. The state revised "the environmental air quality standards" On February 29, 2012. The PM2.5 was incorporated into the scope of mandatory testing. To alleviate the air pollution, gas car has became one of the realistic choice and developed rapid. Measure the LNG liquid level is very important to the gas car of vehicle-mounted LNG tank(cryogenic seal tank). And so on and so forth, the single capacitance measurement need calibration with high cost of manpower and material resources, and the measurement precision is low(linear error is more than 7% ~10%), low precision easy to cause the driver misjudgment on energy consumption and vehicle broke down,. So increasing the LNG measurement accuracy is particularly important.Thesis mainly research the LNG liquid level height measurement to the vehicle-mounted LNG tank. It put forward a new concept of Dual capacitance measurement based on the original single capacitance measurement. The measurement methods effectively improves vehicle-mounted LNG tank level measurement precision(linear error <3%) and breaks through industry development bottleneck. Thesis mainly introduce some aspects as following.(1) The research analyses the reason of single low precision capacitance measurement, and calibration with high waste of manpower and material resources. Put forward Dual capacitance measurement method. Thesis analyzes the reason of the Dual capacitance measurement can improve the accuracy, and Dual capacitance measurement need no calibration.(2) Product improves the structure of the single capacitance measurement, practical application to uses the structure with two capacitances in left and right side by side, improves sensor noise immunity. It analysis how to selection of structural materials and effectively guarantee the stability of the product in the process to suitable the ultra-low temperature environment.(3) The Dual capacitance measurement circuit is designed, Two capacitances will interfere with each other easy because the two capacitances is measured at the same time and produce parasitic capacitance. Analyzing the interference, isolating the circuit. Electrical interface circuit design for lightning and surge protection.(4) From calibration at the scene and compensation's algorithm is put forward, it effectively solve the problems of single LNG capacitance measurement. At the same time the product uses in bumpy car, so effectively filter algorithm in software must be designedFinally through the test and practical application validates the effectiveness of the double capacitance measurement of innovation design. LNG tank Dual capacitance LNG liquid level intelligent sensor research provide a solution of since the compensation, low cost, high precision and high efficiency measurement. The solution as well as provides reliable perception of parts for the networked vehicle intelligent management control system(iot management).